CVE-2017-16099 in no-case
Summary
by MITRE
The no-case module is vulnerable to regular expression denial of service. When malicious untrusted user input is passed into no-case it can block the event loop causing a denial of service condition.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2017-16099 resides within the no-case module, a component commonly used in web applications for case-insensitive string comparisons. This module processes user input through regular expression patterns to perform text matching operations, creating a critical security risk when handling untrusted data. The vulnerability manifests as a regular expression denial of service attack, where specifically crafted malicious input can cause the regular expression engine to enter into a computationally expensive state. This behavior occurs because the regular expression pattern used by no-case contains constructs that are susceptible to catastrophic backtracking, a well-documented vulnerability in regular expression implementations that can cause exponential time complexity during pattern matching operations. The attack vector is particularly concerning as it requires only a single malicious input string to trigger the denial of service condition, making it highly exploitable in environments where user input is not properly sanitized.
The technical flaw within the no-case module stems from the implementation of regular expression patterns that do not account for potential backtracking scenarios that can occur with maliciously crafted input. When untrusted user data is processed through these vulnerable patterns, the regular expression engine can spend excessive computational resources attempting to match the input against the pattern, leading to event loop blocking in Node.js environments where the module is typically deployed. This vulnerability directly maps to CWE-400, which categorizes regular expression denial of service attacks as a form of resource exhaustion that can lead to system instability and service disruption. The operational impact is severe as this vulnerability allows an attacker to consume excessive CPU resources and effectively block the application's event loop, preventing legitimate users from accessing services and potentially causing complete application unavailability. The attack can be executed with minimal effort and can be amplified through multiple concurrent requests, making it particularly dangerous in production environments where the module might be used extensively.
The exploitation of CVE-2017-16099 aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. This vulnerability can be leveraged in various attack scenarios including web application attacks, API endpoint exploitation, and service disruption campaigns. The impact extends beyond simple service disruption as it can affect the entire application stack, potentially leading to cascading failures in systems that rely on the affected module. Organizations running applications that utilize the no-case module are particularly vulnerable, especially those that process user input through this component without proper validation or rate limiting mechanisms. The vulnerability demonstrates the critical importance of input validation and regular expression security practices in modern web applications, as even seemingly benign modules can become attack vectors when not properly secured against malicious input patterns.
Mitigation strategies for CVE-2017-16099 should focus on immediate remediation through module updates or replacements, as the original vulnerable version has been superseded by patched releases. Organizations should implement comprehensive input validation measures that sanitize user data before processing, including length limits and character set restrictions to prevent malicious patterns from reaching the vulnerable regular expressions. Additionally, implementing rate limiting and request throttling mechanisms can help reduce the impact of potential attacks by limiting the number of requests that can be processed within a given time period. The use of alternative string comparison methods that do not rely on regular expressions for case-insensitive matching can provide more secure alternatives. Security monitoring should include detection of unusual processing times or resource consumption patterns that might indicate exploitation attempts. Organizations should also conduct thorough code reviews to identify other instances of vulnerable regular expressions within their applications and implement regular security testing to prevent similar vulnerabilities from being introduced in future development cycles.